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Replacing 38 year old home boiler

My Burnham boiler is 38 years old and still works ok but I think it is about time to replace. I am told it's efficiency is only in the 60 percent range. There are so many makes and models so I am looking for guidance. The present boiler is vented to a chimney but I am considering a direct vent in order to make the chimney available for a wood burner. What is better, a condensing or a non-condensing boiler? stainless or cast iron burners? smart controls or standard? how high efficiency should I get? how many BTUs do I need.

My fuel is natural gas. The house is 2 story 2400 square feet with about 16" of fiberglass insulation in the attic. All windows are double pane and most of them also have an outside storm window. I live in northern Ohio.

I prefer to buy made in USA. Because I have had good service from the Burnham I am leaning in that direction. What do you recommend?

I really like triangle tube condensing boilers but if you have fin tube you won't get the efficiency out of it because it wont condense at the temps you need. I good 87% cast boiler direct vent would be perfect for that. If you have low temp applications a condensing is good.

I really like triangle tube condensing boilers but if you have fin tube you won't get the efficiency out of it because it wont condense at the temps you need. I good 87% cast boiler direct vent would be perfect for that. If you have low temp applications a condensing is good.

My radiators are 3/4" copper with fins. The boiler heats the water to 180 F. I don't know the temp of the return water. Can this setup run at a lower temperature where the condensing boiler is efficient?

Absolutely, with an outdoor reset control the system wouldn't produce high temperature water on mild days that still require heating. These temperatures would certainly be in the condensing range on those days. Contrary to popular belief outdoor reset and condensing boilers both work with fin tube baseboard, while there are other methods of radiation that are better suited for ODR and mod con boilers baseboard still works with it.

I think something to consider with any HVAC system, about 3/4 of the time you only need approx. 50% of the total design capacity. So you should be able to run lower water temps most of the time, except at evening and nightime during the coldest 4-6 weeks of winter. Set-up perfectly, the boiler runs almost continously (depending on turn down) and just modulates water temp to match the heat loss. OF coruse that's why proper sizing is improtant fo both the radiators, piping and boiler to make it work best.

We set the boiler minimum at around 140, below that fin tube is a lot less effective. We have had problems with to low of temps and even in our mod con training classes they address these issues. In five years or more when a part goes bad on a mod con you better open up your wallet. A cast iron boiler with outdoor reset would be great. I think opinions will vary though.

Not to belittle American made products but our European and Asian counterparts are far ahead of us in technology and pricing which is a sad statement to make. While everyone has their favorite brands that work well the installation practices are far more important than the boiler however if you get a great contractor with a great product it is a win win. I personally recommend the navien line of combination boiler/on demand water heater although others have had great luck with other products. Best of luck

We'll just see if the Navien tankless I have will operate trouble free for 25 years like any of these older "inferior" designed boilers and wall hung boilers.

I can't verify if useage has increased, but I have yet to see any savings going to tankless. It appears any efficiency and standby loss gain I made have been completely offset by using a recirulation loop. SO I'm trading some efficiency for comfort. That's OK with me overall. I suppose you could argue I've gone from a well insulated 40 gallon tank, to a moderately insulated 2-3 gallons worth of piping which probably had 3X the total surface area as the larger tank.

First, you'll have to have an accurate heat loss calculation done on your house to determine how many btu's you need. Do NOT, repeat, Do Not size the new boiler based on the size of the old one - it's probably well over-sized. If the contractor won't do a heat loss (manual J or equivalent) on the envelope, send him packing. He's either lazy or doesn't know what he's talking about. Then measure the lineal footage of your baseboard elements. If it's standard 7" baseboard, multiply the total length of the elements (not the enclosures) by 500 to get the output capacity of the radiation. It will probably be higher than your calculated heat loss. If so, that's a good thing. The greater the radiation is over-sized, the more the supply temp can be lowered and the more efficient the boiler will operate.

Second, A mod/con will work great with baseboard because the outdoor reset, when properly set, will keep it condensing most of the time. It is true that mod/cons can be costly to repair, but so can cast iron boilers. I just came from one where we replaced the electronic flue damper, relief valve, gauge, installed an MBR and isolation valves and it was not cheap.

As far as a brand goes, it's far more important to get a competent installer than a particular make of boiler. If you choose a mod/con, the stainless steel down fired are the best: TT., Lochinvar WH, or ECR Dunkirk, Utica wall hung. I would not recommend anything that incorporates a Gianonni heat exchanger. They require a lot of maintenance and will fail quickly if fouling or scaling occurs. Buderus is down fired with an aluminum heat exchanger.

If you choose to go cast iron, the Buderus is unequaled, but almost any other would be good.

Bob Boan

​You can choose to do what you want, but you cannot choose the consequences. ​